That's not difficult for a technical person. Even for non-technical people, Google provides great tools for going from iOS to Android.
Hardware
Mac -> Windows PC
iPhone -> Android phone
iPad -> Android tablet or a very huge Android phone
Apple Watch -> Wear watch or Samsung watch
Apple TV -> Chromecast or a smart TV
Airport -> any network router
Apple Magic Keyboard -> any Bluetooth keyboard
Apple Magic Mouse -> any Bluetooth mouse
Files and iCloud Drive
Method 1: Copy files from iCloud Drive and local file system to OneDrive/Google Drive/Dropbox
Method 2: Create a shared drive in Windows and copy files directly from the Mac to the PC
Method 3: Copy files from iCloud Drive and local file system to a USB drive, copy from USB drive to Windows PC
iCloud Photo Library
Method 1: Have Google Photo getting all the photos and uploading them to Google Photo
Method 2: Open Photos on the Mac, select all photos and videos, export to Windows share, USB drive or even directly to OneDrive/Google Drive/Dropbox folder on the Mac
Method 3: Open iCloud.com on your PC, open iPhotos, select all the photos, download them to the Windows PC
Photos without iCloud Photo Library
Method 1: Open Photos on the Mac, select all photos and videos, export to Windows share, USB drive or even directly to OneDrive/Google Drive/Dropbox folder on the Mac
Method 2: Enable iCloud Photo Library and use the methods for iCloud Photo Library
iCloud emails
Method 1: Open gmail.com, import emails directly from iCloud from there
Method 2: Use any IMAP-enabled mail client on the Mac or Windows, open your iCloud account in said mail client, upon another IMAP account (Gmail, Outlook.com etc.) and copy each folder manually with drag and drop
iCloud contacts
Method 1: Open gmail.com, import contacts directly from iCloud from there
Method 2: If you're using something else like outlook.com, you can use Method 1, then export as CSV and import to outlook.com and others
Method 3: Open icloud.com and Contacts, select all contacts, export as VCF, use spreadsheet or website to convert from VCF to CSV, open outlook.com, import the CSV from there
Apple Music
Use Spotify.
If you need to transfer playlist, use utilities like Tune My Music, Soundiiz or even a free service such as
https://playlists.cloud
Notes
Method 1: Use Exporter from Mac App Store
Method 2: Install OneNote on the Mac, sync Notes through iCloud, for every single note share it to OneNote
Method 3: Use "Obtain your data" service from Apple
iMessages
Method 1: Use a third-party application on Mac or PC, e.g. iMazing, TextMessage, TenorShare
Method 2: Use a third-party solution from Github, usually free like iMessage-exporter
Non-Apple Software
Almost all software is available on Windows and Android.